When boats have AIS trans on board, is it linked to the radio, or is it on its own switch. ie: does a boat with radio tuned off also mean the AIS is inactive as well.

Hello,

This can be accomplished one of two ways. In both cases it is not necessary to have the VHF radio on for the AIS to transmit.

1. The AIS has its own stand alone antenna. If the AIS is on, it's working.

2. The AIS and VHF share an antenna, utilizing a splitter. Vesper marine makes a good one. The splitter does need 12vdc. The way that I have wired it is to have the AIS, splitter and VHF on the same breaker. This way, the VHF can be turned off at the radio itself, but the AIS functions normally.

When boats have AIS trans on board, is it linked to the radio, or is it on its own switch. ie: does a boat with radio tuned off also mean the AIS is inactive as well.

For what it's worth, I have a Vesper XB-8000 on the same panel switch as the VHF radio. Partly, because I ran out of spare panel switches and partly because it just makes sense to have both on at the same time.

__________________
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When boats have AIS trans on board, is it linked to the radio, or is it on its own switch. ie: does a boat with radio tuned off also mean the AIS is inactive as well.

Chrisgo,

Others have provided you with qualified detailed answers.

I wanted to mention we often use our AIS transceiver independent of the VHF radios- mainly when we are sleeping at anchor.

When we anchor, I change the status in the AIS software to "Anchored."

This summer we had an experience that reinforced this habit: We were in a sleepy little bay that had what appeared to be an inactive logging operation at its head.

At 0400 the next morning the radar proximity alarm got me up in time to see a very large barge ghosting past us in the fog not 100 feet away. [They had no choice but to transit between us and a small island...] When the fog lifted later that morning I could see the barge being loaded with logs...

Would they have seen us anyway? Most likely: we were also lighted beyond the mast-top anchor light, and have a very good radar reflector high on the main mast. However, I feel better knowing that they knew precisely where we were, what we are, and that we were at anchor, many miles before they arrived...

This is our main reason for operating our AIS transceiver independent of the VHF radios.

AIS is the next best thing after the invention of the anchor, I wouldn't leave the dock without one.

It's one thing to see a dot on the radar screen coming toward you on a collision course, and call out "little dot that's about to hit me come in", and have 5 ships answer is it me? while YOU try to sort out which of the many ships you are talking to, and which one is about to collide, It's entirely another to to get an AIS alarm, "The shipping vessel 200' Freighter Coal dancer 1, (GPS Lat long, DSC ID number #123432 on a course 189 at 22kts will intercept in 5 mins".

I've found when you call out a tug, or large freighter, and try to get an answer by mile marker, or vessel description, (assuming you can actually see it), they rarely will answer.

BUT when you call the ship by name, or enter it's DSC code, they ALWAYS answer.

in our case with a professionally installed system, our Garmin 600 transceiver is powered up to transmit whenever there is power to the NMEA 2000 backbone, so in our case when the instruments breaker is 'on' and we have windspeed/direction/boatspeed/depth as well as the plotter/radar MFD. and autopilot. THe VHF is powered separately from it's own breaker switch but the masthead VHF aerial is shared with the AIS even though the VHF itself may not be switched off.

As an aside we also have an AIS transmit 'off' switch because turning AIS display off on the MFD does not stop AIS data transmission, only display of targets rec'd

The advice for installing VHF is that it should be either wired direct to the batteries or to the master fire switch with it's own fuse - no breaker or on/off Sw - I other words, if the boat has power VHF is on. This meets the requirement to keep a listening watch at all times when underway. Underway includes anchored in a fairway
I apply the same to the AIS.

You have a class A transceiver? This is not an option for the majority of the recreational AIS units.

Mark

Hi Mark,

Sorry, I forgot to mention which AIS came with the boat:

Class B Vesper Watchmate 850.

Your question prompted me to consult the manual. It appears I have misunderstood the Anchored 'Profile' setting in that it in fact does not set the [non-existent in Class B AIS, as you correctly pointed out] Navigation Status field to Anchored.

All the Anchored profile does is pre-select [user settable] filter settings desired for monitoring other AIS targets when at anchor. [e.g., Fewer or no alarms, etc.]

Therefore we are not broadcasting our Navigation Status as I had mistakenly thought.

Thank you for pointing out my misunderstanding. I guess I hadn't realized Class B AIS had this limitation...

Since we leave our AIS on when at anchor we are still broadcasting our position, etc. but not broadcasting being at anchor- leaving it to any interested party to discern our status from the AIS data received.

At least they will [hopefully] still see us ahead of time.

Next time I'm on the boat I'll temporarily remove our boat's MMSI from the MFD to perceive our vessel as a target and scrutinize the data from the perspective of an approaching vessel. [Lesson learned: Something I didn't think of when testing/validating AIS function when I bought the boat last year...]

I also forgot to mention in my earlier post in this thread another reason we separate AIS from VHF [per OP's initial question] is to take advantage of the marvelous anchor alarm built-into this AIS unit [VHF is off when sleeping at anchor...]

Therefore we are not broadcasting our Navigation Status as I had mistakenly thought.

Thank you for pointing out my misunderstanding. I guess I hadn't realized Class B AIS had this limitation...

FWIW, my NN3D display of Furuno FA-150 Class A AIS does not display anchored vessels any differently than those underway (except that the status is burried in the details), so I suspect that the barge was no less likely to see you as a result of this Class B limitation.

FWIW, my NN3D display of Furuno FA-150 Class A AIS does not display anchored vessels any differently than those underway (except that the status is burried in the details),

Yes, that is a frustrating limitation of the Furuno NN3D - it pretty much sucks at AIS presentation, and is very basic at best.

OCPN, Coastal Explorer and many iPad apps show anchored vessels distinctly marked (as well as other special types, like limited steerage, etc). Other MFD's also have better presentation than Furuno NN3D.

Let me add one item about AIS friend of mine got boarded by Venezuelan misfits on the way to Trinidad from Grenada. They pistol whipped him and mishandled his petite wife stole some items and left. He was 40 miles off chaguaramas by the oil rigs. Apparently they had picked up his AIS transmission so they knew what they were after. Sailors with AIS transmitters be wary bad guys close to you are watching and listening.

I don't think this will work because your Vesper is feeding the MFD the AIS data, and it knows to internally ignore ownship MMSI.

Mark

Hi Mark,

I believe you are correct if we could only use the Vesper as our AIS Rx data source.

However, since we standardized on AIS based MOB alarm devices [SafeLink R10] we have chosen to have redundant AIS receivers. [The Vesper Transceiver and AIS Rx built into one of the VHF radios. The AIS outputs seem to always be in parity sans any filter settings we make in the Vesper...]

We can choose which input source to use on the MFD. [B&G Zeus T8]

Perhaps because of this, B&G provided some settings to accommodate 'dumb' AIS receivers in that you can input your vessel's MMSI# into the MFD to prevent you from appearing as another AIS target. [Ironically its the B&G VHF that isn't smart enough to ignore us...]

Therefore, using the VHF as the AIS Rx source, and removing our MMSI from the MFD settings will allow us to view our AIS Tx data as another vessel does... [At least this is how it all behaved before a fairly recent firmware update for the B&G VHF; the one fixing the random switching to the Wx channel- and other irritations...]

This may be a useful test case... or not... we will find out in a few weeks when I return to the boat.